The translucency of zebrafish embryos and larvae makes them ideally suited for the in vivo analysis of developmental and physiological processes. This study aims to develop tools for the multicolor fluorescent labeling of zebrafish cells. Previous studies have demonstrated that stochastic DNA recombination can lead to the expression of different combinations of fluorescent proteins in different cells. The combinatorial expression of fluorescent proteins endows cells with many colors, thereby providing a way to distinguish adjacent cells and visualize cellular interactions. We will develop tools that make this technology widely and easily applicable to the study of zebrafish development and anatomy (Aim 1) and generate next-generation reagents and protocols that allow the sophisticated application of this technology to various aspects of zebrafish biology (Aim 2). PUBLIC HEALTH RELEVANCE: Zebrafish is a vertebrate model organism that shares many biological processes with humans. Research in zebrafish has provided important insights into the causes of birth defects and disease. The proposed work is to enhance the utility of this model system by developing tools to label cells in multiple different colors and follow their development.